This invention relates to condition-sensitive timing controls, and particularly to timers for systems which take one action in response to a cyclically recurring physical condition and another on the basis of a timing arrangement.
A typical application for such a device occurs in regulation of outdoor lighting equipment that is intended to illuminate an area during its normally used evening or nighttime hours. An example of a location where such control would be desirable is a parking lot of a shopping mall.
Condition-sensitive timing controls may be used to start air cooling systems or heating systems at sunrise and end their operation during the night.
One type of outdoor lighting equipment regulator is interposed between current carrying lines and a load. It is composed of a sensitive element that causes a relay to permit actuation of the lights at sunset in response to the diminishing ambient sunlight. At sunrise the photocell responds to the increasing ambient light and causes the relay to cut off power to the lighting equipment. Such devices are satisfactory but tend to waste substantial amounts of current during the early morning hours when the illuminated area is not used. Such type of device is also unsuitable for starting and stopping the aforementioned air cooling systems.
One available type of device is capable of solving the problem of energy waste in an outdoor lighting system by energizing the light only for a predetermined period of time after sunset. Such a system could be used for starting an air cooling operation at sunrise. However, such a system fails to consider changes in the times of sunrise and sunset throughout the year. If, during the summer, the timing mechanism used is set to turn off lights five hours after a 9 P.M. summer sunset, the same timing mechanism would extinguish the light five hours after a 5 P.M. winter sunset, namely at 10 P.M. Such a system is not completely satisfactory if the illuminated facilities are to be used to a specific hour. On the other hand, accommodating the timing mechanism to a 5 P.M. winter sunset, so that it would extinguish the lights nine hours later at the desired time of 2 A.M., would result in illumination throughout the night and after sunrise during the summer months.
An object of this invention is to improve controls of this type.
Another object of this invention is to alleviate the aforementioned difficulties.